Song Young-gil, a former leader of the main opposition Democratic Party, was turned away Wednesday after he voluntarily appeared at a prosecutor's office for questioning over a cash-for-vote scandal involving his campaign ahead of the party's 2021 leadership election.

Upon arriving at the Seoul Central District Prosecutors Office, Song asked for a meeting with prosecutors investigating the scandal, but was denied. Song plans to stage a standalone protest in front of the prosecution office later in the day.

It marks the second time Song has been turned away after making a voluntary appearance without a summons to do so. Right after his return from France, Song appeared at the prosecution office on May 2, but prosecutors turned him away, saying a questioning had not been scheduled.

Song was suspected of involvement in a scandal that centers on allegations that his campaign distributed cash envelopes totaling 94 million won ($72,385) to 10-20 Democratic Party lawmakers and other party members in the run-up to the party's leadership election in May 2021, which he ultimately won.

Prosecutors recently sought arrest warrants for two former Democratic Party lawmakers -- Youn Kwan-suk and Lee Sung-man -- on charges of involvement in the campaign, and a motion requesting parliament's consent for their potential arrest was reported to a plenary parliamentary session last week.

A vote on the motion is scheduled for June 12.

Earlier this week, prosecutors also raided the National Assembly Secretariat in search of the entry and exit logs of sitting lawmakers in connection with the scandal.

Prosecutors reportedly plan to summon Song for questioning in the final stage of the investigation after completing its probe into others. (Yonhap)